A bromine tungsten filament lamp is a large kind of light source for modem lighting, and most of service voltages of bromine tungsten filament lamps are low voltage of 12 V. Therefore, when 120V/50 Hz or 220V/50 Hz power supply is adopted, transformer must be used. At present there are two kinds of transformers for bromine tungsten filament lamps. One is iron-core transformer and the other electronic transformer. The advantage of the former is simple circuit, but the disadvantages are high consumption, heavy weight and large size. For higher power, the disadvantages are more obvious. The advantages of the latter are low consumption, small size and light weight. Therefore, the electronic transformer of bromine tungsten filament lamp has been extensively used. The principle of frequency conversion and voltage transformation is applied to electronic transformer, which is composed of rectification filter circuit, frequency conversion circuit and high-frequency transformer. The frequency of electronic transformer is 20-60 Khz. The development of modern lighting requires multi-region directional lighting, so one electronic transformer of bromine tungsten filament lamp is required to have the function of being used by several bromine tungsten filament lamps. Meanwhile a certain length of output feeder line must be used. But because the working frequency of bromine tungsten filament lamp is rather high, the transmission impedance of output feeder line itself is low. The impedance is close to that of bromine tungsten filament lamp. Besides, in installation, the length of feeder line and distance between lines are not fixed by the user and the number of bromine tungsten filament lamp not fixed either. Therefore, the serious mismatched output will occur. Practice shows that when the output is mismatched, the output power is lowered and the luminance lowered too. In the most serious case, the frequency conversion switching transistor of the frequency converter will be burnt. If the number of installed lamps is rather small, the load is less than nominal power and the lamps will be overpowered, their life shortened and the switching transistor burnt. On account of the above causes, the current electronic transformer of bromine tungsten filament lamp sold in the market cannot be connected with output feeder line.